The MDT (modular formation dynamics tester, trademark of Schlumberger Technology Corporation) is routinely run on TLC (tough logging conditions system, trademark of Schlumberger Technology Corporation) to perform mini DSTs (mini Drill Stem Tests).
U.S. Pat. No. 6,092,416 entitled “Downhole system and method for determining formation properties” describes a drill pipe or tubing attached to a sampling tool that is suspended in a borehole. A wireline cable also connects the tool to surface equipment and establishes electrical communication between the tool and the surface equipment. A valve located in the docking head assembly controls fluid flow between the borehole and the drill pipe through a port located within the drill pipe assembly which is opened and closed as required. During operations, the tool takes fluid samples from the formation and analyzes them for contamination levels. Unacceptable fluid is pumped or flowed through the tool via a flowline and into the drill pipe where it is stored until it is disposed of at the surface. Once the flowing fluid reaches acceptable levels of contamination, this fluid is pumped or flowed into one or more sample chambers in the tool. Once sampling is completed, the contaminated fluid is forced to the surface by opening the port and pumping a different fluid down the borehole annulus, through the port, and into the tool below the contaminated fluid, and thereby filling the drill pipe and forcing the contaminated fluid up the drill pipe and to the surface, instead of discarding the fluid into the borehole or storing the fluid in the tool. This system allows for larger amounts of fluid to be retrieved from the formation which results in cleaner fluid samples and better information about the formation. Moreover, the nature of the pressure data acquired both during periods of flow and shut-in can be used to deduce formation permeability and permeability anisotropy.
Patent Application Pub. No. WO2008/100156 entitled “Assembly and Method for Transient and Continuous Testing of an Open Portion of a Well Bore” discloses an assembly for transient and continuous testing of an open portion of a well bore. The assembly is arranged in a lower part of a drill string, and comprises: a minimum of two packers fixed at the outside of the drill string, the packers being expandable for isolating a reservoir interval; a down-hole pump for pumping formation fluid from the reservoir interval; a mud driven turbine or electric cable for supplying energy to the down-hole pump; a sample chamber; sensors and telemetry for measuring fluid properties; a closing valve for closing the fluid flow from the reservoir interval; and a circulation unit for mud circulation from a drill pipe to an annulus above the packers and feeding formation fluid from the down-hole pump to the annulus. The sensors and telemetry are for measuring and real-time transmission of the flow rate, pressure, and temperature of the fluid flow from the reservoir interval, from the down-hole pump, in the drill string, and in an annulus above the packers. The circulation unit can feed formation fluid from the reservoir interval into the annulus, so that a well at any time can be kept in over balance and so that the mud in the annulus at any time can solve the formation fluid from the reservoir interval.
The entire disclosures of U.S. Pat. No. 6,092,416 and Patent Application Pub. No. WO2008/100156 are incorporated herein by reference.